Are you sure the compost is done? That seems pretty quick for 20 worms unless you have like a handfull of food in there?

I have Compost going right now that is like 8 or 9 months old and the worms are still working away at it slowly. I think a lot or all of them were dead then new eggs hatched. There aren't very many but it's a lot more than 20 in there.

Not exactly sure how big a worm factory is size wise - my experience is that you lose some of the worms in the transition and if the space is too large they may be too spread out for rapid reproduction - I started with about 500 worms in a 1 gallon planter bin - after 1 month had lots of babies and split into 2 planters and so on. I would try putting them in a smaller container inside the worm factory (like a butter tub) with bedding and food and see if they don't do better.

Last spring I lost a large portion of my herd to overheating. I threw some cooked rice in there, and it cooked the majority of the worms.

Was the bin covered with anything over the newpaper? Could they have crawled out?
Terry

Worms have a natural need to want to travel when a fast moving storm front comes through. Probably to avoid drowning in the rain. You might have had some travelers. I have had entire beds get up and leave all at once in just a few mins. The only thing they fear more is light and will not travel in light, even a small one.